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Tuesday - September 28, 2010

From: Georgetown, TX
Region: Southwest
Topic: Trees
Title: Pollenless Cedar Elms for Georgetown, Texas
Answered by: Marilyn Kircus


I am considering planting the Cedar Elm tree at my home in Georgetown, Texas. I was under the impression that only the female of the species produces the irritating pollen. Is this true?


No, pollen is a guy thing.  Pollen contains the male gametes and is analogous to sperm in animals.   Females produce the irritating things known as kids. (For plants, the strategy is to produce them as seeds and not have to incubate them internally for nine months.)  Plants can be him (male) or her (female) or them (both male and female)."Them" kinds of plants can be further divided into those who have both male and female flowers and those who have flowers that contain both male and female parts.  The latter are called bisexual, hermaphroditic or perfect flowers. When flowers of both sexes are on the same plant, it is called monoecious. When the sexes are on two different plants, the species is described as dioecious.

Ulmus crassifolia (Cedar elms) are wonderful shade trees.  They are recommended as a good substitute for oaks since they don’t get oak wilt. I love their yellow fall color. They are used by lots of different wildlife. Their flowers are perfect and are wind pollinated.  They bloom in late summer and fall - usually August to October and their pollen does cause allergies in some people.  Here is more information on them.

So in addition to having perfect flowers, I think it is a pretty perfect tree.

I'm wondering if maybe you are thinking about the pollen problems with Juniperus ashei (Ashe juniper), a.k.a. cedar. These trees ARE dioecious and the cedar pollen is profuse and will travel long distances.  And of course, there are lots of them. This is the pollen that causes the most allergy trouble in central Texas. But it's the guys plants causing the problem.  The girls have the pretty berries.



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